Lip fou



March 24, 1964 LIP FOU WONG ETAL 3,126,214

DIVERGENT METAL THREADED AND SHRUNK FIT PIPE COUPLING 2 Sheets-Sheet 2 L/p 10w: Permwyfon E/wn G. fio/ce f/mer Vo/merf INVENTORJ ATTO/F/VEKJ F00 Wong United States PatentOfiice 3,126,214 Patented Mar. 24, 1964 DIVERGENT METAL THREADED AND HRUNK FIT FEE CUUPLING Lip Fou Wong, enrico County, and Louis E. Pennington, Chester-field Gninty, Va, and Elvin G. Boice and Eimer J. Volmert, Houston, Tex.; said Wong and said Pennington assignors to Reynolds Metals (Ionipany, Richmond, Va., a corporation of Delaware, and said Boise and said Volmert assignors to Reed Roller Bit (Ionrpany,

Houston, Tex., a corporation of Texas Filed May 16, 1960, Ser. No. 29,199 7 Claims. (Cl. 285-173) This invention relates generally to pipe couplings, and more particularly to tool joints for aluminum alloy drill pipe.

In conventional deep well drilling, the Well drill string comprises a plurality of steel pipe sections connected together by threaded steel couplings which are known as tool joints. The drill string serves to raise, lower or drive a drill bit (not shown) connected to the lower end thereof and serves to conduct drilling fluid to the bottom of a bore hole to remove cuttings dislodged by the drilling operation.

The weight of a steel drill string for a deep well is tremendous, and the resulting problems in transporting the pipe to and from the well and in manipulating the pipe in the well are many and well known to those skilled in the art but for many years have remained unsolved. The use of steel drill strings has also created other problems which remain unsolved; for example, many well surveying instruments such as directional orientation instruments and the like cannot be operated at different elevations within the drill string in the well because of the magnetic properties in the string.

The general object of this invention is to provide a new and improved drill string which does not have the tremendous weight of the drill strings heretofore used nor the magnetic properties thereof and is otherwise superior to the conventional drill strings.

More specifically, the invention has for its object to provide a drill string comprising aluminum alloy pipe connected by steel tool joints, the pipe and joints being so combined as to alleviate failures in the pipe in the area of the last engaged thread and in the area adjacent the pipe end of the tool joint.

Another object is to provide a new and improved method of assembling the pipe and joints, whereby the tool may be readily assembled to provide an enduring connection.

Other objects will become apparent from the following description and the accompanying drawings of the preferred embodiment of the invention in which:

FIG. 1 is an elevation view, partly in section, of a threaded coupling for a drill string.

FIG. 2 is a vertical sectional View of an end of a drill pipe section showing schematically an air hammer which may be used to peen a portion of the pipe section adjacent to its threaded portion.

FIG. 3 is an enlarged sectional view of a tool joint memben;

FIG. 4 is a sectional view of a tool joint member and an end of a pipe section showing schematically a method for cooling the pipe section and the tool joint member.

Referring to FIG. 1, a steel tool joint coupling is shown generally at A comprising a tool joint pin member 1 and a tool joint box member 2. The tool joint members 1 and 2 are screwed together by means of the threaded portions 3. Aluminum alloy pipe sections are shown at 4. Since the manner of securing the pipe section 4 into the tool joint members 1 or 2 is the same, a description of one will describe the other.

The pipe 4 is externally threaded as indicated at 5. The tool joint member 2 is also provided with threads as shown at 6 which interengage with the threads 5 of the pipe section 4. The tool joint member 2 has an internal circumferential land 7. The pipe 4 has an external circumferential land 8 which is adjacent to the threaded portion 5 and registers with the land 7 of the tool joint member 2.

Referring more particularly to FIG. 3, the tool joint member 2 is shown in enlarged detail. The threaded area 3 may comprise tapered threads of an American Petroleum Institute standard form. The thread 6 may be of a modified acme form of 6 threads per inch on /8 inch taper per foot or any other suitable thread form. The tool joint member 2 has a smooth circumferential land 7 adjacent the threads 6 and the outer end 9 of the tool joint member 2. The tool joint member 2 has a bore 10 so that drilling fluid may be circulated therethrough. The external surface of the tool joint member 2 may be tapered as indicated at 11 to accommodate elevators (not shown) for raising and lowering the drill string into the bore hole. The taper at 11 is in the order of magnitude of 18 and is helpful in providing a more gradual transfer of the stress to the aluminum alloy pipe by avoiding an abrupt change of section. The outer end of the tool joint member 2 is radiused as indicated at 12. The tool joint member 2 is provided with a radially inwardly extending shoulder 13. The axial extent of the internal land 7 is made unusually long when compared to a typical design for a steel tool joint member for use with steel pipe. This unusual length is provided to avoid rupture of the aluminum alloy pipe in the tool joint member because of the presence or" the last engaged thread which acts as a stress raiser for the pipe. In the embodiment shown, the axial extent of the internal land 7 has a dimension which is greater than the dimension of the radius to the outside of the drill pipe 4.

Referring to FIG. 2, the circumferential land 8 of the pipe section 4 is smooth and is peened to work-alter the same, as by peening with a reciprocating pneumatic hammer as shown at 14, or by rolling the land 8, or in any other suitable manner. The work-altering of the land 8 is preferably extended beyond the end 9 (shown in phantom) of the tool joint member 2 for a distance of approximately /2 inch to 1 inch as shown at B. The end 15 of the pipe section 4% is provided with a smooth finish to effect a seal by engagement with the radially inwardly extending shoulder 13.

The aluminum alloy pipe section 4 may be made of various aluminum alloy materials such as 2014-T6 or 7075T6 as designated by the Aluminum Association, or of any other suitable non-ferrous alloy. It has been found that in order to Withstand the fatigue loading to which the pipe is subjected that the pipe sections 4 may be made by an extrusion process, preferably by a continuous extruded process, in which thickened ends are provided on the pipe. The thickened end of the pipe made by such a process accommodates the external threads 5 and the work-altered land 8. The inside diameter 19 of the'pipe section thus formed is substantially uniform. Thus, there is no obstruction to the flow of drilling fluid to the bottom bore hole. The transition zone C of the taper from the nominal outside diameter of the body of the pipe to the outside diameter of the Workaltered land portion 8 is unusually long to avoid an abrupt change in cross section. In the actual drill pipe assembly, taper Zones of between 25 and 35 inches have been used. The tool joint members 1 and 2 may be made of SAE 4140 steel or the like.

Referring to FIG. 2, the thickened end of the pipe section 4 is threaded as indicated at 5. The land 8 is formed and peened to provide an outside diameter of the land portion 8 which is initially approximately .010 to .016 inch larger than the inside diameter of the land '7 f the tool joint member 2 thereby providing for an interference'fit in the assembled coupling of that amount. For example, the land portion 8 may be machined to produce a surface finish of approximately 60 to 100 micro-inches. The pipe section may then be rotated approximately 8 to 12 revolutions per minute and the pneumatic hammer 14 then engaged with the land 8 to peen the same to alter the surface thereof. The axial movement of the hammer 14 with respect to the land 8 is preferably 30 to 40 micro-inches. The pneumatic hammer 14 may have, for example, a working piston of approximately one inch in diameter and may be supplied with air of 60 to 70 p.s.i.

To assemble the tool joint member 2 on the pipe section 4, the pipe section 4 is inclined dowwardly as shown in FIG. 4. A plug 16, which may be composed of a resilient material such as rubber or the like, is inserted into the end of the pipe section 4. The tool joint member 2 is heated to a temperature of approximately 650 F. by means of a gas-fired tool joint heater or in any other suitable manner. The heating of the tool joint member 2 causes it to expand radially and axially so that it may be installed on the threaded and land portions of the pipe section 4. A coolant, such as water or the like, is supplied to the interior of the pipe section 4 by means of a hose 17. The hot tool joint member 2 is then screwed upon the pipe section 4 until the end 15 of the pipe section 4 engages the shoulder 13 of the tool joint member 2. The tool joint member 2 is then cooled such as by water issuing from a spray head 18. The cooling of the tool joint member, after it has been thus assembled, causes it to shrink upon the end of the pipe section 4 whereupon the internal land 7 of the tool joint member 2 Will engage with and compress the external land 8 of the pipe section 4. The axial shrinking of the tool joint member 2 will compress the end 15 of the pipe section 4 with the annular shoulder 13 of the tool joint member 2. Cooling of the pipe section 4 by means of the water hose 17 is effected during the assembly operation. The plug 16 prevents the pipe cooling water from coming into contact with the hot tool joint member 2. The aluminum alloy pipe is a very good conductor of heat and it is essential that the pipe be cooled to prevent a loss of strength therein by virtue of its exposure to elevated temperatures. Thus, the temperature of the pipe section 4 is preferably maintained below 180 F. during the assembly operation.

This invention is not limited to the embodiment shown. Other embodiments within the scope of the following claims will occur to those skilled in the art.

What is claimed is:

1. A drill pipe threaded coupling comprising a lightweight per unit length non-ferrous alloy pipe member of a given wall thickness in the body having an end portion whose wall is thicker than said body portion,

external threads on said thickened end portion,

a circumferential land having a work-altered external surface on said thickened end portion between the threads and said body portion and extending to an area adjacent said external threads,

a ferrous metal tool joint member having an internal threaded portion in engagement with the external threads of said pipe member and an internal circumferential land adjacent the outer end of the said tool joint member and overlapping a portion of the workaltered section on said pipe member,

said work-altered portion extending toward the body beyond said tool joint land, the outside diameter of the said work-altered pipe land being slightly greater initially than the inside diameter of said tool joint land,

said pipe and tool joint member being secured together in such manner that hoop stress is developed between said lands.

2. The coupling of claim 1 wherein the tool joint member has a radially inwardly extending annular shoulder near the inner portion of said internal threads, and the end surface of said pipe member lies against said annular shoulder.

3. The coupling of claim 1 wherein the end of said tool joint member which overlaps said pipe land has a tapered external annular surface of about 18 with respect to the longitudinal axis of said tool joint member.

4. The coupling of claim 1 wherein the interior peripheral surface of said tool joint member which overlaps said pipe land is radiused.

5. The coupling of claim 1 wherein the land on said pipe member is initially machined to a desired diameter and then work-altered by peening, and wherein the workaltered land is initially .010 to .016 inch greater in size than the inside diameter of the said tool joint land.

6. The method of making a coupling for lightweight per unit length non-ferrous alloy pipe of a given body Wall thickness having an end with a thicker wall, including,

providing external threads on the end of said pipe and a smooth land on said thicker wall, said land being removed from the end of the pipe and adjacent the threads,

work-altering the external surface of said land on said p pe.

forming an internal threaded socket in a ferrous metal tool joint member and a smooth land adjacent the outer end of said socket slightly smaller than said pipe land,

heating the said tool joint member,

screwing the tool joint member on the pipe until the threads are made up and a portion of the Workaltered land extends outwardly beyond the tool joint land,

continuously cooling the pipe land and threads while the joint is being made up,

and upon said joint being made up immediately subjecting said tool joint member to a cooling medium while continuing to cool the pipe to generate a hoop stress in the joint.

7. The method of claim 6 wherein the step of cooling the tool joint member is carried out by a spray of liquid.

References Cited in the file of this patent UNITED STATES PATENTS 1,776,615 Boothman Sept. 23, 1930 2,122,757 Scott July 5, 1938 2,267,339 Paulsen Dec. 23, 1941 2,418,418 Martin et al. Apr. 1, 1947 2,636,753 Gritfin Apr. 28, 1953 

1. A DRILL PIPE THREADED COUPLING COMPRISING A LIGHTWEIGHT PER UNIT LENGTH NON-FERROUS ALLOY PIPE MEMBER OF A GIVEN WALL THICKNESS IN THE BODY HAVING AN END PORTION WHOSE WALL IS THICKER THAN SAID BODY PORTION, EXTERNAL THREADS ON SAID THICKENED END PORTION, A CIRCUMFERENTIAL LAND HAVING A WORK-ALTERED EXTERNAL SURFACE ON SAID THICKENED END PORTION BETWEEN THE THREADS AND SAID BODY PORTION AND EXTENDING TO AN AREA ADJACENT SAID EXTERNAL THREADS, 